The technique of IVF has been used in human patients with infertility problems successfully since 1978. Despite extensive research it is still a difficult procedure and even in the best IVF clinics a success rate of only 30% is generally achieved.
IVF is an expensive procedure and can also be psychologically traumatic for a patient. Surgical procedures are required to collect eggs for IVF and following fertilization, further surgery is required to implant fertilised eggs in the womb. The recipient must then wait for a period of time before it can be determined whether or not pregnancy has been established. In some cases, pregnancy may never be established despite repeated attempts and these cases represent a considerable expense to society, both in financial and human terms.
Therefore, until success rates of IVF can be improved, it would be desirable to be able to identify recipients for whom IVF is unlikely to be successful prior to treatment, so that such patients avoid the abovementioned costs of the IVF procedure.
The adrenal steroid hormone, cortisol, is believed to influence maturation of the female germ cell (the oocyte) and the development of ovarian cells in culture (Orly & Sato (1979) Cell 17,295; Patino & Thomas, (1990) J. Exp. 2006 255,97). Recently, Fateh et al (1989, Fertil. Steril. 51,538-541) have reported that there is an association between the concentration of cortisol in follicular fluid and oocyte maturity.
The enzyme 11.beta.-hydroxysteroid dehydrogenase (EC 1.1.1.146) converts cortisol to its inactive form, cortisone. Benediktsson et al (J. Endocrinology (1992) 135, 53-58) report the presence of 11.beta.-hydroxysteroid dehydrogenase (11.beta.-HSD) in rat oocytes. The results of Benediktsson et al suggest a role for 11.beta.-HSD in modulating ovarian function. Two isoforms of 11.beta.-HSD have been characterised; a hepatic form and a renal form. Our initial findings suggest that both isoforms are expressed in ovarian tissue. In the present invention, reference to 11.beta.-HSD includes both isoforms.